title: Clinical predictive value of manual muscle strength testing during critical illness: an observational cohort study.
abstract: BACKGROUND
  Impaired skeletal muscle function has important clinical outcome implications for survivors of critical illness. Previous studies employing volitional manual muscle testing for diagnosing intensive care unit-acquired weakness (ICU-AW) during the early stages of critical illness have only provided limited data on outcome. This study aimed to determine inter-observer agreement and clinical predictive value of the Medical Research Council sum score (MRC-SS) test in critically ill patients.
  
  
  METHODS
  Study 1: Inter-observer agreement for ICU-AW between two clinicians in critically ill patients within ICU (n = 20) was compared with simulated presentations (n = 20). Study 2: MRC-SS at awakening in an unselected sequential ICU cohort was used to determine the clinical predictive value (n = 94) for outcomes of ICU and hospital mortality and length of stay.
  
  
  RESULTS
  Although the intra-class correlation coefficient (ICC) for MRC-SS in the ICU was 0.94 (95% CI 0.85-0.98), κ statistic for diagnosis of ICU-AW (MRC-SS <48/60) was only 0.60 (95% CI 0.25-0.95). Agreement for simulated weakness presentations was almost complete (ICC 1.0 (95% CI 0.99-1.0), with a κ statistic of 1.0 (95% CI 1.0-1.0)). There was no association observed between ability to perform the MRC-SS and clinical outcome and no association between ICU-AW and mortality. Although ICU-AW demonstrated limited positive predictive value for ICU (54.2%; 95% CI 39.2-68.6) and hospital (66.7%; 95% CI 51.6-79.6) length of stay, the negative predictive value for ICU length of stay was clinically acceptable (88.2%; 95% CI 63.6-98.5).
  
  
  CONCLUSIONS
  These data highlight the limited clinical applicability of volitional muscle strength testing in critically ill patients. Alternative non-volitional strategies are required for assessment and monitoring of muscle function in the early stages of critical illness.
authors.forename: Bronwen A
authors.initials: BA
authors.lastname: Connolly
authors.forename: Gareth D
authors.initials: GD
authors.lastname: Jones
authors.forename: Alexandra A
authors.initials: AA
authors.lastname: Curtis
authors.forename: Patrick B
authors.initials: PB
authors.lastname: Murphy
authors.forename: Abdel
authors.initials: A
authors.lastname: Douiri
authors.forename: Nicholas S
authors.initials: NS
authors.lastname: Hopkinson
authors.forename: Michael I
authors.initials: MI
authors.lastname: Polkey
authors.forename: John
authors.initials: J
authors.lastname: Moxham
authors.forename: Nicholas
authors.initials: N
authors.lastname: Hart
mesh_terms: D018806:APACHE; D000368:Aged; D016638:Critical Illness; D005260:Female; D017052:Hospital Mortality; D006801:Humans; D007362:Intensive Care Units; D007902:Length of Stay / Q000706:statistics & numerical data; D008297:Male; D008875:Middle Aged; D018908:Muscle Weakness / Q000503:physiopathology*; D011237:Predictive Value of Tests; D014474:Unconsciousness / Q000503:physiopathology